Holiday homework worksheet for Grade 8A on Pongal holidays, featuring animal illustrations for a dichotomous key exercise.

Let’s solve this step by step.

We are asked to construct a dichotomous key for the 7 animals labeled A through G.
A dichotomous key is like a decision tree — at each step, you choose between two options (yes/no or this/that) until you identify the animal.

First, let’s look at what each animal is:

- A: Frog (smooth skin, no tail, big eyes)
- B: Snake (long, no legs, scales)
- C: Salamander (has tail, smooth skin, small limbs)
- D: Lizard-like but with black head? Wait — actually, looking closely, D has a long body and tail, but also has limbs → likely another type of lizard or amphibian. But note: it has a distinct black head — maybe a newt or salamander variant? Actually, in biology keys, we focus on physical traits, not color unless specified. Let’s assume all are reptiles/amphibians.
Wait — better approach: group them by major features.

Let’s list observable traits:

1. Has legs? Or no legs?
- No legs: B (snake)
- Has legs: A, C, D, E, F, G

2. Has tail?
- With tail: C, D, G
- Without tail: A, E, F

3. Skin texture?
- Smooth/moist (amphibians): A, C, E, F
- Scaly/dry (reptiles): B, D, G? Wait — D looks smooth too? Hmm.

Actually, let’s use standard biological classification clues for these types of animals.

Common way to start:

→ Step 1: Does the animal have legs?

If NO → It’s B (snake)

If YES → Go to next question.

Now among those with legs:

→ Step 2: Does it have a tail?

If YES → C, D, G

If NO → A, E, F

Now split the “with tail” group:

→ Step 3: Is the body long and slender with short legs? (like a lizard) OR more robust?

But D has a very long body and tail, small legs — could be a skink or similar.

G is spotted, long tail, four legs — looks like a gecko or lizard.

C is smoother, less scaly — probably a salamander.

So perhaps:

For “has tail”:

→ Step 3a: Skin smooth and moist? → C (salamander)

→ Step 3b: Skin dry/scaly? → then check further.

Between D and G:

D has uniform color except black head — but since color isn’t reliable, maybe body shape.

D is very elongated, almost snake-like but with tiny legs.

G is shorter-bodied, spotted.

Alternatively, count toes? Not visible.

Better idea: Use presence of external gills or other features? Not shown.

Perhaps simpler:

After “has tail”, ask:

→ Are the limbs well-developed and obvious?

G has clear limbs.

D has very small limbs — might be considered reduced.

But still tricky.

Alternative path: Start with habitat clue? Not given.

Let’s try building the key logically from top down.

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Step-by-step construction:

Start with most obvious difference: presence of legs.

1a. Animal has no legs → B

1b. Animal has legs → go to 2

Now, among legged animals, separate by tail.

2a. Animal has no tail → go to 3

2b. Animal has tail → go to 4

Group without tail: A, E, F — all frogs/toads.

How to tell them apart?

Look at body shape:

- A: rounder body, bumpy skin? (toad?)
- E: flatter, wider body
- F: smoother, larger eyes, tree frog type?

In many keys, they use:

→ Toe pads? F has large toe pads (tree frog)

→ Skin texture: A may be warty, E smooth?

But images are grayscale.

Assume:

F has enlarged toe tips → tree frog

E has broad flat body → bullfrog or similar

A is more typical frog/toad

So:

3a. Toes have large sticky pads → F

3b. Toes do not have large pads → go to 3c

3c. Body rounded and bumpy → A

3d. Body flat and wide → E

Now back to tailed group: C, D, G

All have tails and legs.

C: smooth skin, aquatic-looking → salamander

D: very long body, small legs, uniform except head → possibly a legless lizard? But it has legs! So maybe a skink.

G: spotted, normal lizard proportions.

So:

4a. Skin smooth and moist (amphibian) → C

4b. Skin dry and scaly (reptile) → go to 5

Then between D and G:

5a. Body extremely elongated, limbs very small → D

5b. Body proportionate, limbs normal size → G

That works.

Let’s write the full key neatly.

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Final Dichotomous Key:

1. a. Animal has no legs → B
b. Animal has legs → go to 2

2. a. Animal has no tail → go to 3
b. Animal has tail → go to 4

3. a. Toes have large adhesive pads → F
b. Toes lack large pads → go to 3c
c. Body rounded and bumpy → A
d. Body flat and broad → E

4. a. Skin smooth and moist → C
b. Skin dry and scaly → go to 5

5. a. Body very long and slender, limbs tiny → D
b. Body normally proportioned, limbs obvious → G

This covers all 7 animals uniquely.

Double-check:

- B: no legs → correct
- A: legs, no tail, no pads, bumpy → yes
- E: legs, no tail, no pads, flat → yes
- F: legs, no tail, has pads → yes
- C: legs, tail, smooth skin → yes
- D: legs, tail, scaly, long body → yes
- G: legs, tail, scaly, normal body → yes

Perfect.

Final Answer:
1. a. Animal has no legs → B
b. Animal has legs → go to 2
2. a. Animal has no tail → go to 3
b. Animal has tail → go to 4
3. a. Toes have large adhesive pads → F
b. Toes lack large pads → go to 3c
c. Body rounded and bumpy → A
d. Body flat and broad → E
4. a. Skin smooth and moist → C
b. Skin dry and scaly → go to 5
5. a. Body very long and slender, limbs tiny → D
b. Body normally proportioned, limbs obvious → G